The present invention relates to a water removing device for removing water contained in a refrigerant in a refrigerating system used in an air conditioner or the like.
When water is mixed in a refrigerant, it causes various inconveniences such as internal corrosion of a metallic portion which is in contact with the refrigerant, deterioration of the cooling performance due to freezing in an expansion device, and a trouble of a compressor caused by the compression of liquid. In an automobile air conditioner, since rubber hoses are used in various portions for absorbing vibration, water is apt to enter the refrigerant through those rubber hoses. Japanese Patent Laid Open No. 157462/84, shows that a refrigerant is cooled by a cold trap using liquid nitrogen to cool the refrigerant and freeze water contained in the refrigerant, then the water is removed.
However, the cold trap requires a cooling device for obtaining the liquid nitrogen at ultra-low temperature and hence it has been difficult to provide the cooling device in a limited mounting space
Japanese Patent Laid Open No. 146477/90, shows another refrigerating system wherein a refrigerant is branched from a refrigerant pipe in a portion which becomes high in both temperature and pressure due to compression by a compressor and the thus-branched refrigerant is cooled by the refrigerant whose temperature became low in an expansion valve. A water recovering device is provided in the portion where the branched refrigerant is cooled, whereby the water dissolved in the refrigerant is separated and recovered by glass wool. In this refrigerating system Freon-12 (CFC-12) is used as refrigerant, which has a property such that the higher the temperature, the larger the amount of water dissolved therein, and a saturated water concentration is higher in gas phase than in liquid phase.
In such refrigerating system, however, it is necessary to pass a branch pipe for cooling through an outlet side portion of the expansion valve and connect a return pipe to an inlet side portion of the same valve. There have been problems; for example, the laying of the branch pipe is difficult, and the conditions for heat exchange to remove water in the water recovering device are changeable depending on various factors, including whether the cooling load is large or small, so it is difficult to set a cooling area of the refrigerant. In other words, in the refrigerating system in question, water is removed only under specific conditions, while under other conditions the removal of water is not effected smoothly.
In such refrigerating system, moreover, there has been a problem such that in the case of using a refrigerant, for example Freon-134a (HFC-134a), Freon-22 (CFC-22) which is higher in saturated water concentration in liquid phase than in gas phase, contrary to Freon-12, there is not obtained a satisfactory water removing performance. More particularly, even if water which could be separated from a liquid refrigerant by branching and cooling is recovered completely by glass wool, water will be formed and freeze in a gaseous refrigerant which is formed after adiabatic expansion in the expansion valve, thus causing inconvenience.
Further, in the water separating device disclosed in Japanese Patent Laid Open No. 287066/90, an opening is formed in part of the peripheral wall of a refrigerant circulating passage, and a water permeating membrane which permits only the water contained in a refrigerant to pass therethrough is disposed in the said opening. Also disposed in the opening is a casing, with a desiccant contained therein.
In such water separating device, since water is recovered from only the refrigerant which is in contact with the water permeating membrane, there arises the necessity of enlarging the area of the opening in order to enhance the water recovering efficiency. However, even if the opening is made large, the separation of water is not so effective because the water permeating membrane is disposed in parallel with the refrigerant flowing direction and further because water passes in a dissolved state in the refrigerant.